Linking Cancer Metabolism to DNA Repair and Accelerated Senescence.

Unlabelled: Conventional wisdom ascribes metabolic reprogramming in cancer to meeting increased demands for intermediates to support rapid proliferation. Prior models have proposed benefits toward cell survival, immortality, and stress resistance, although the recent discovery of oncometabolites has shifted attention to chromatin targets affecting gene expression. To explore further effects of cancer metabolism and epigenetic deregulation, DNA repair kinetics were examined in cells treated with metabolic intermediates, oncometabolites, and/or metabolic inhibitors by tracking resolution of double-strand breaks (DSB) in irradiated MCF7 breast cancer cells.

Identification of fumarate hydratase inhibitors with nutrient-dependent cytotoxicity.

Development of cell-permeable small molecules that target enzymes involved in energy metabolism remains important yet challenging. We describe here the discovery of a new class of compounds with a nutrient-dependent cytotoxicity profile that arises from pharmacological inhibition of fumarate hydratase (also known as fumarase). This finding was enabled by a high-throughput screen of a diverse chemical library in a panel of human cancer cell lines cultured under different growth conditions, followed by subsequent structure-activity optimization and target identification.

Silver-Promoted Benzannulations of Siloxy Alkynes with Pyridinium and Isoquinolinium Salts.

We describe the development of efficient benzannulations of siloxy alkynes with pyridinium and isoquinolinium salts. Such reactions are successfully promoted by a stoichiometric amount of silver(I) benzolate under mild reaction conditions. This process proceeds via a formal inverse-electron demand Diels-Alder reaction, followed by fragmentation of the initially produced bicyclic adducts to deliver a range of synthetically useful phenols and naphthols.

[2+2+2] Cycloadditions of siloxy alkynes with 1,2-diazines: from reaction discovery to identification of an antiglycolytic chemotype.

Cycloaddition uncovered: The title reaction produces novel polycyclic compounds with high efficiency and excellent diastereoselectivity under mild reaction conditions. A small-molecule library, synthesized using this reaction, yielded a novel chemotype which inhibited glycolytic ATP production by blocking glucose uptake in CHO-K1 cells. DMF=N,N-dimethylformamide, Tf=trifluoromethanesulfonyl, TIPS=triisopropylsilyl.

Emulating the logic of monoterpenoid alkaloid biogenesis to access a skeletally diverse chemical library.

We have developed a synthetic strategy that mimics the diversity-generating power of monoterpenoid indole alkaloid biosynthesis. Our general approach goes beyond diversification of a single natural product-like substructure and enables production of a highly diverse collection of small molecules. The reaction sequence begins with rapid and highly modular assembly of the tetracyclic indoloquinolizidine core, which can be chemoselectively processed into several additional skeletally diverse structural frameworks.

Label-assisted mass spectrometry for the acceleration of reaction discovery and optimization.

The identification of new reactions expands our knowledge of chemical reactivity and enables new synthetic applications. Accelerating the pace of this discovery process remains challenging. We describe a highly effective and simple platform for screening a large number of potential chemical reactions in order to discover and optimize previously unknown catalytic transformations, thereby revealing new chemical reactivity.

Assembly of four diverse heterocyclic libraries enabled by Prins cyclization, Au-catalyzed enyne cycloisomerization, and automated amide synthesis.

We describe a unified synthetic strategy for efficient assembly of four new heterocyclic libraries. The synthesis began by creating a range of structurally diverse pyrrolidinones or piperidinones. Such compounds were obtained in a simple one-flask operation starting with readily available amines, ketoesters, and unsaturated anhydrides.

Silver-catalyzed formal inverse electron-demand Diels-Alder reaction of 1,2-diazines and siloxy alkynes.

A highly effective silver-catalyzed formal inverse electron-demand Diels-Alder reaction of 1,2-diazines and siloxy alkynes has been developed. The reactions provide ready access to a wide range of siloxy naphthalenes and anthracenes, which are formed in good to high yields, under mild reaction conditions, using low catalyst loadings.

Three-component reaction discovery enabled by mass spectrometry of self-assembled monolayers.

Multicomponent reactions are employed extensively in many areas of organic chemistry. Despite significant progress, the discovery of such enabling transformations remains challenging. Here, we present the development of a parallel, label-free reaction-discovery platform that can be used in the identification of new multicomponent transformations.

Chemical synthesis enables biochemical and antibacterial evaluation of streptolydigin antibiotics.

Inhibition of bacterial transcription represents an effective and clinically validated anti-infective chemotherapeutic strategy. We describe the evolution of our approach to the streptolydigin class of antibiotics that target bacterial RNA polymerases (RNAPs). This effort resulted in the synthesis and biological evaluation of streptolydigin, streptolydiginone, streptolic acid, and a series of new streptolydigin-based agents.

Creation and manipulation of common functional groups en route to a skeletally diverse chemical library.

We have developed an efficient strategy to a skeletally diverse chemical library, which entailed a sequence of enyne cycloisomerization, [4 + 2] cycloaddition, alkene dihydroxylation, and diol carbamylation. Using this approach, only 16 readily available building blocks were needed to produce a representative 191-member library, which displayed broad distribution of molecular shapes and excellent physicochemical properties. This library further enabled identification of a small molecule, which effectively suppressed glycolytic production of ATP and lactate in CHO-K1 cell line, representing a potential lead for the development of a new class of glycolytic inhibitors.

A pairwise chemical genetic screen identifies new inhibitors of glucose transport.

Oxidative phosphorylation (OXPHOS) and glycolysis are the two main pathways that control energy metabolism of a cell. The Warburg effect, in which glycolysis remains active even under aerobic conditions, is considered a key driver for cancer cell proliferation, malignancy, metastasis, and therapeutic resistance. To target aerobic glycolysis, we exploited the complementary roles of OXPHOS and glycolysis in ATP synthesis as the basis for a chemical genetic screen, enabling rapid identification of novel small-molecule inhibitors of facilitative glucose transport.

Synthesis of streptolydigin, a potent bacterial RNA polymerase inhibitor.

Streptolydigin is a highly potent, broad-spectrum antibiotic produced by Streptomyces lydicus, which inhibits bacterial RNA polymerase. We describe the first synthesis of streptolydigin, which was assembled in a highly convergent and fully stereocontrolled fashion with a longest linear sequence of 24 steps starting from commercially available precursors. The assembly process entailed preparation of fully elaborated streptolic and ydiginic subunits of the natural product, followed by a highly efficient union in a three-step one-pot procedure, which included Dieckmann cyclization with a concomitant imide opening, Horner-Wadsworth-Emmons olefination, and desilylation.

Synthesis of a high-purity chemical library reveals a potent inducer of oxidative stress.

Synthesis of high-purity biogenic heterocyclic library enabled identification of a small molecule, which potently inhibited proliferation of several cancer cell lines and induces rapid oxidative stress. This agent elicited unusual mechanism of cell death induction, which entailed activation of both caspase-dependent and independent pathways.

Rationally simplified bistramide analog reversibly targets actin polymerization and inhibits cancer progression in vitro and in vivo.

We describe structure-based design and chemical synthesis of a simplified analog of bistramide A, which potently and reversibly binds monomeric actin with a K(d) of 9.0 nM, depolymerizes filamentous actin in vitro and in A549 (nonsmall cell lung cancer) cells, inhibits growth of cancer cell lines in vitro at submicromolar concentrations, and significantly suppresses proliferation of A549 cells in a nude mice tumor xenograft model in terms of both tumor growth delay and average tumor volume. This study provides a conceptual framework for the design and development of new antiproliferative compounds that target cytoskeletal organization of cancer cells in vivo by a combination of reversible G-actin binding and effective F-actin severing.

Silver-Catalyzed Aldehyde Olefination Using Siloxy Alkynes.

We describe the development of a silver-catalyzed carbonyl olefination employing electron rich siloxy alkynes. This process constitutes an efficient synthesis of trisubstituted unsaturated esters, and represents an alternative to the widely utilized Horner-Wadsworth-Emmons reaction. Excellent diastereoselectivities are observed for a range of aldehydes using either 1-siloxy-1-propyne or 1-siloxy-1-hexyne.

Synthesis of an azide-tagged library of 2,3-dihydro-4-quinolones.

We describe the assembly of a 960-member library of tricyclic 2,3-dihydro-4-quinolones using a combination of solution-phase high-throughput organic synthesis and parallel chromatographic purification. The library was produced with high efficiency and complete chemo- and diastereoselectivity by diversification of an azide-bearing quinolone via a sequence of [4 + 2] cycloadditions, N-acylations, and reductive aminations. The azide-functionalization of this library is designed to facilitate subsequent preparation of fluorescent or affinity probes, as well as small-molecule/surface conjugation.

Identification and characterization of a small molecule inhibitor of formin-mediated actin assembly.

Formins stimulate actin filament assembly for fundamental cellular processes including division, adhesion, establishing polarity, and motility. A formin inhibitor would be useful because most cells express multiple formins whose functions are not known and because metastatic tumor formation depends on the deregulation of formin-dependent processes. We identified a general small molecule inhibitor of formin homology 2 domains (SMIFH2) by screening compounds for the ability to prevent formin-mediated actin assembly in vitro.

Synthesis enables identification of the cellular target of leucascandrolide A and neopeltolide.

Leucascandrolide A and neopeltolide are structurally homologous marine natural products that elicit potent antiproliferative profiles in mammalian cells and yeast. The scarcity of naturally available material has been a significant barrier to their biochemical and pharmacological evaluation. We developed practical synthetic access to this class of natural products that enabled the determination of their mechanism of action.

The dual mode of action of bistramide A entails severing of filamentous actin and covalent protein modification.

This study provides comprehensive characterization of the mode of action of bistramide A and identifies structural requirements of bistramide-based compounds that are responsible for severing actin filaments and inhibiting growth of cancer cells in vitro and in vivo. We rationally designed and assembled a series of structural analogs of the natural product, including a fluorescently labeled conjugate. We used TIRF microscopy to directly observe actin filament severing by this series of small molecules, which established that the combination of the spiroketal and the amide subunits was sufficient to enable rapid actin filament disassembly in vitro.

Au- and pt-catalyzed cycloisomerizations of 1,5-enynes to cyclohexadienes with a broad alkyne scope.

We describe the development of gold- and platinum-catalyzed cycloisomerizations of 1,5-enynes. This catalytic process displays a wide alkyne scope and furnishes a range of highly functionalized 1,4- and 1,3-cyclohexadienes. In the case of 1-siloxy-1-yne-5-enes, the reactions are efficiently catalyzed by AuCl (1 mol %) at ambient temperature to afford siloxy cyclohexadienes or the corresponding 1,2- and 1,3-cyclohexenones upon subsequent protodesilylation.

Structure of bistramide A-actin complex at a 1.35 angstroms resolution.

Bistramide A is a highly potent antiproliferative marine natural product from Lissoclinum bistratum. We have previously established actin as the primary cellular receptor of bistramide A. We report herein the X-ray structure of bistramide A bound to monomeric actin at a resolution of 1.